The database is located on a Server2003 operating system and they access it using a mapped drive. Anybody had this issue before?
Why is it on a mapped drive? If the file is shared between simultaneous users, they should access this via open remote and this does not require a shared/mapped drive. The file should be hosted with filemaker Pro or filemaker server on the remote machine.
Problems can occur if two users try to open a file in a shared folder directly at the same time. Open Remote is designed to protect against those problems.